An actuator of an electromechanical parking brake of a vehicle includes a motor and a power transmission unit for operating a friction pad installed at a caliper of a disc brake assembly during the vehicle parking.
For example, if a driver pushes a parking brake switch, the rotating force of the motor of the actuator is transmitted to an input shaft of the caliper through a power transmission unit such as a reducing gear. The rotation of the input shaft allows a pressurizing junction sleeve to advance, and the advancing of the pressurizing junction sleeve allows a piston received therein and a caliper housing to move closer to each other, so that two friction pads mounted to the piston and the caliper housing press both sides of the disc so that the disc is restricted not to rotate.
Patent documents 1 to 3 disclose various examples of the actuator of an electromechanical parking brake.
A traditional parking brake uses a cable-operating manner in which a driver pulls a cable to operate a friction pad or a brake lining.
In place of it, existing electromechanical parking brake actuators such as those disclosed in Patent documents 1 to 3 have been adopted to give convenience to a driver since a parking brake is operated by a motor.
The electromechanical parking brake gives convenience to a driver as described above. However, since a device of a new type is mounted, a vehicle designer encounters unfamiliar vibration and noise caused by the device. For this reason, a high-quality vehicle which winds the confidence of drivers may be provided when a study for regulating or removing such vibration and noise is accompanied.
For example, in an actuator for an electromechanical parking brake, the rotating force of a motor is transmitted to a planetary gear set through a power transmission gear or a power transmission belt, and the input shaft of a caliper rotates by the rotation of the output shaft of the planetary gear set.
In this power transmission process, together with vibration and noise caused by the operating motor, there are generated vibration, noise and strange sound due to collision, friction or backlash between gear teeth surfaces, which are also propagated out of the housing.
In addition, if the parking brake is not in operation, the vibration generated by an engine of a vehicle may be transferred to an actuator housing and cause resonance. The resonance of the actuator housing is harsh to the ear and may also be propagated to other surrounding elements to cause an unusual noise not experienced before.
Meanwhile, in order to improve convenience in assembly or supply of components or in order to reduce costs or improve productivity in this connection, a so-called ‘modularized’ manufacturing method in which various components are assembled in a sub-assembly form in advance to be handled as a single element is recently introduced to a vehicle.
If the parking brake actuator is modularized, a motor and a power transmission unit may be supplied as a single assembled module and thus they need not be newly assembled in a vehicle manufacturing factory. Therefore, this may give various advantages such as simplifying the vehicle assembling process and facilitating easier supply and management of components.
However, as another purpose for modularizing the actuator, the processes of producing and assembling actuator components may be entrusted to a specialized company so that the study for improving quality may be intensively performed.
The quality of the actuator naturally includes the quality in relation to vibration and noise as described above. Therefore, the study for minimizing vibration and noise and the study for designing a structure for modularization should be performed together and harmonized.